Light weight structural materials

ABSTRACT

Functionalized microspheres for being dispersed in matrix materials to reduce the density and weight of the materials may be configured to include a covalently bound surface component which is configured to covalently bond with the matrix material so that when combined with the matrix material a strong, light-weight matrix material may be produced.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage filing under 35 U.S.C. §371 ofInternational Application No. PCT/US2013/023996 filed Jan. 31, 2013entitled “LIGHT WEIGHT STRUCTURAL MATERIALS,” which is incorporatedherein by reference in its entirety.

BACKGROUND

For most products which are to be handled and/or carried by consumers,the consumer typically prefers lighter weight products while not wantingto lose any product quality or durability. Lighter weight products, inaddition to being more desirable for consumers, are often also preferredby manufactures in order to reduce shipping and handling costs.Essentially everything from raw materials and parts to finished productsneed to be shipped from their point of origin to the consumer.

Energy is required to move an object, whether that object is in agravitational field or not. In a gravitational field an object hasweight, and outside a gravitational field an object has mass. It takesfuel to move an object from a point A to a point B. Energy is requiredto accelerate the object to get it moving, and also to sustain the speedof movement according to the relationship mass times velocity squared.The energy needed to move an object may be expressed in terms of watts,where a watt is the ability to lift one kg one meter in one secondagainst the force of gravity.

It also takes energy to hold an object against the force of gravity.Fuel is required to supply the energy. For vehicles, such as ships andtrains, the fuel is typically a hydrocarbon mixture. For a human beingor other animal, the fuel is glucose, and for a rocket, the fuel isoften liquid oxygen and liquid hydrogen. The heavier the object the morefuel it takes to move the object. In addition, for the human body, thenecessity of carrying around heavier objects may lead to added sorenessin the shoulders and spine. Thus, there is a need for lighter weightobjects that are essentially as strong and durable as the heavierobjects that are being replaced.

Other issues may also arise from the selection of the types of materialsused for product production. Electronic products are constantly beingimproved and upgraded, and environmental impacts can result from thelarge volumes of consumer electronic products that enter into and phaseout of the market each year. Certain materials used to produce productsfor consumers and industries require manufacturing processes that areenergy intensive and generate large amounts of greenhouse gas andenvironmental waste. In addition, many waste products end up inlandfills, and the materials may persist in the environment forthousands of years.

Therefore, there is an increased need for ultra-lightweight materialsthat are not energy intensive to produce, and which are easy to recycleand preferably biodegradable, but significant technological needs remainunmet. New lightweight and ultra-lightweight materials are needed thatare durable (i.e. impact-, crack-, rupture-, fatigue-, andcorrosion-resistant), formable, transparent, non-toxic, inexpensive tofabricate, manufactured using low environment impact processes, andbiodegradable. For certain applications, improved thermal conductivity,electrical conductivity, and optical transparency may also be relevant.Materials having reduced density/weight would be useful for applicationsin space, aerospace, vehicles, industrial products, consumer products,and everyday life in the human world.

SUMMARY

Presently disclosed are ultra-strong lightweight materials whichincorporate hollow microspheres that have been treated in a manner thatallows the spheres to be covalently bound within the material. Thehollow microspheres reduce the density/weight of the product, while thecovalent bonding between the spheres and the material provide a threedimensional bonded network to increase the structural integrity of thematerial. As an example, in an embodiment, ceramic microspheres may befunctionalized by covalently bonding epoxy polymerizable groups to themicrospheres, and a light weight epoxy product may be made by mixing thefunctionalized microspheres with an epoxy resin, followed by hardeningof the resin so that the microspheres are covalently bound within theresin, take up a volume portion of the resin and thereby reduce thedensity/weight of the resin.

In an embodiment, functionalized hollow microspheres are provided forreducing the density of structural matrix materials. The microspheresinclude covalently bonded functional groups selected to covalently bondwith the structural matrix material.

In an addition embodiment, a low-density material includes hollowmicrospheres covalently bonded with structural matrix material.

In a further embodiment, a method for producing a low density structuralmaterial includes intermixing hollow microspheres with a structuralmatrix material, wherein the hollow microspheres include a functionalgroup selected to covalently bond with the structural matrix material,and covalently bonding the hollow microspheres with the structuralmatrix material.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B depict microspheres embedded in matrix materialsaccording to an embodiment.

FIG. 2 depicts an example of functional components for a microsphereaccording to an embodiment.

FIG. 3 shows a representation of a functionalized microsphere accordingto an embodiment.

FIG. 4 is a schematic representation of a method for producingfunctionalized microspheres according to an embodiment.

DETAILED DESCRIPTION

Materials which have high strength, while also being lightweight, mayprovide many benefits and be advantageous in several ways. Suchmaterials may reduce fuel costs since the objects weigh less and morecan be shipped with a given amount of fuel. In addition, vehicles usedto ship products may weigh less, and as such may carry more and requiresless energy to propel. Thus, lighter weight materials may potentiallyhave great benefits to the carbon footprint and the environment.Consumers generally prefer lighter weight objects that replace commonlyused heavier objects, and often may equate a better quality feel to alighter feel. Carrying lighter objects around may have less wear andtear on the body, and because of this, consumers may feel better andless stressed.

Microspheres may be used to reduce the density, and therefore also theweight of manufactured items by inclusion of the microspheres in thestructural material of the item. The microspheres may be hollow,air-filled microspheres, or may contain a fill which has a lower densitythan the structural material into which they will be incorporated. Somelow-density materials may include foams or other lattice type materialswhich are substantially air filled. For example, hollow microspheres maybe used as additives in concrete to lighten the concrete and protect therebar that reinforces the concrete. Concrete is very heavy and dense andfor certain objects, such as oil platforms, it may be advantageous thatthe concrete be lightened to reduce the weight of the platform, maketransport of the platforms more feasible, and enhance performance.

If non-functionalized hollow microspheres 5 (in FIG. 1A) are simplymixed into material components 7, the spheres typically just blend inlike a pigment and do not contribute to the overall structure. Thespheres 5 are essentially only present within the material 7, and oftenwhen the material cures, dries, or hardens, the material may contractand pull away from the included spheres, leaving a small void space 8between the hollow sphere and the surrounding media. This void space 8may lead to a weakened structure for certain applications. However, asdepicted in FIG. 1B, by covalently binding a functional compound X tothe surface of a hollow sphere 10 to form functionalized spheres 15,such void spaces may be eliminated as the spheres may be covalentlybound with the material 7 via the functional component. A more detailedembodiment of a functionalized sphere 15 is depicted in FIGS. 3 and 4.

Incorporation of functionalized hollow microspheres 15 into structuralmatrix materials may allow the creation of extremely strong yetlightweight structures. In an embodiment, lightweight, low-densitymaterials may be made which include hollow microspheres that arecovalently bonded with the structural matrix material to produce athree-dimensional structural network. As used herein, structuralmaterials, or matrix materials, or structural matrix materials refer toany type of material which may be produced in a non-solidified form andwhich may then harden, or cure to form a structural component, oranother solidified material.

Some examples of structural matrix materials that are used for producinga solidified material include, but are not limited to thermoplasticresins, thermoset resins, inorganic matrices, and cementitious matrices.For example, epoxy resins or polyethylene terephthalate are used to makeplastic components, such as housing, containers, and covers etc. Someexamples of thermoplastic resins may include, but are not limited topolyvinyl chloride, polyethylene, polypropylene, polyethyleneterephthalate, acrylic resin, acetal resin, nylon,polytetrafluoroethylene, urethane, urea resin, carbonate resin, sulfoneresin, cyclic resin, polybutylene terephthalate, other rigid engineeringpolymers, and any combinations thereof. Some examples of thermosetresins may include, but are not limited to polyester, vinylester, epoxyresin, acrylic resin, phenolic resin, sulfone resin,phenyl-formaldehyde, melamine, melamine-formaldehyde, other rigidthermoset engineering polymers, and any combinations thereof. Someexamples of inorganic matrices may include, but are not limited toceramic, glass, glass-ceramic, sol-gel compositions, and anycombinations thereof. Some examples of cementitious matrices mayinclude, but are not limited to portland cement, gypsum, polymermodified cement, latex modified cement, epoxy cements, othercementitious materials commonly used in the manufacture or repair ofconcrete structure, and any combinations thereof.

Microspheres may be functionalized in accordance with the type ofmaterial into which they will be incorporated so that the microspheresinclude covalently bonded functional groups that are configured tocovalently bond with the structural matrix material. When configuredappropriately for a specific matrix material, functionalized spheres 15may be incorporated into a very wide variety of different types ofstructural, or matrix materials 7. The functional compound X, anembodiment of which is depicted in FIG. 2, may be specificallyconfigured to be able to polymerize with the matrix material 7 to form acontinuous material network 50, as depicted in FIG. 4. The hollowspheres 10 may thereby be incorporated into the complete structuralnetwork 50 where the spheres may then contribute to the overall strengthand physical nature of the network. The tightly interwoven network 50may have distinct advantages when subjected to various stresses fromtemperature fluctuations, flexing, stretching, and/or impacting thenetwork. Due to the added strength of the covalent network, the materialwill be able to take physical stresses that simple blended systems areunable to take.

Materials incorporating the covalently bound microspheres may have anincrease in strength of at least about 5% as compared with materialswhich have non-covalently bound microspheres. The percent increase instrength may depend on the number of functional groups present on themicrospheres, the types of functional groups, the strength of thecovalent bonds being formed, and the percent volume of spheresincorporated into the material. For various embodiments, the increase instrength may be about 5% to about 10%. In other embodiments, theincrease in strength may be about 10% to about 15%, or about 15% toabout 20%, or may even be greater than about 20%. On a weight-for-weightbasis, some materials incorporating the covalently bound microspheresmay be at least about 35% stronger. In addition, further embodiments maybe about 35% to about 40% stronger, or about 40% to about 50% stronger,or may even be greater than about 50% stronger.

The hollow microspheres 10 may be constructed from a variety ofdifferent materials. Some examples of the materials from which thehollow spheres may be constructed include, but are not limited toinorganic solids, such as ceramic, glass, metal, metalloids, andcombinations thereof, carbon compositions (all allotropes), organicpolymers, and plastics. Spheres of lighter weight materials, such asplastics, may provide a greater reduction in weight than microspheres ofa heavier material, such as ceramics. Some examples of microsphereswhich may be functionalized in accordance with embodiments include thefollowing microspheres manufactured by 3M™ of St. Paul, Minn.: CeramicMicrospheres: W-210 size 0.3-12 microns; W-410 size 0.3-24 microns;W-610 size 0.3-40 microns; W-273 size 1-9 microns; and Glass Bubbles:A16/500 density 0.16 grams per cubic centimeter, size 30-95 microns(10^(th)-90^(th) percentiles); A20/1000 density 0.20 g/cc, size 25-60microns (10^(th)-90^(th) percentiles); D32/4500 density 0.34 g/cc, size20-65 microns (10^(th)-90^(th) percentiles); H50/10,000 EPX density 0.50g/cc, 15-55 microns (10^(th)-90^(th) percentiles). In addition, themicrospheres may be hollow polyethylene microspheres of about 50 micronsin diameter and about 5-10 microns wall thickness.

Functional compound X may be configured in accordance with the chemicalnature of the matrix material 7 to covalently bond with the matrixmaterial and form a structural network 50 as discussed above. For thispurpose, functional compounds X may be configured to include at least afunctional group, that may be organic or inorganic, and that iscompatible with, and bondable with the matrix material 7. Some examplesof functional groups may include, but are not limited to acrylates,methacrylates, ethacrylates, 2-phenyl acrylates, acrylamides,methacrylamides, cyanoacrylates, epoxies, oxetanes, vinyls, vinylethers, vinyl esters, vinyl amides, vinyl ketones, styrenes, styryls,isocyanates, uranyls, carboxyls, olefins, allyls, allyl ethers, allylesters, allyl amines, allyl amides, ethynyls, propargyls, acryloyls,methacryloyls, maleic anhydride, maleic esters, maleimides, itaconates,silanes, siloxanes, silanols, titanates, thiols, phosphazines, titaniumoxides, silicones, zirconium oxides, and any combinations thereof.

In an embodiment, as depicted in FIG. 2, in order to attach thefunctional group with the microspheres, a bonding agent may also beneeded. Such a bonding agent may covalently bond with both themicrosphere and the functional group to attach and retain the functionalgroup with the microspheres. The bonding agent may have an anchoringcomponent which is compatible with, and configured to chemically bind tothe microspheres by covalent bonds. The covalent bonds with the surfaceof the hollow microspheres provide for continuity between the spheres,the functional compounds X, and the surrounding matrix material 7. As anexample of the number of binding sites available, for microspheres ofabout 30 microns in diameter, the available surface area will be about376800 nm² (surface area of a sphere is 4πr², 1 micron=1000 nm). Thus,there may be about 376,800 functional units per sphere or 6.25×10⁻¹⁹mol.

Some examples of anchoring groups may include, but are not limited toalcohols; amines; thiols; thiosulphates; carboxylic acids; acidchlorides; esters; acetals; hemiacetals; aminals; hemiaminals; ketones;aldehydes; α-hydroxy ketones; α-halo ketones; epoxides; lactones;thiolactones; azalactones; isocyanate; thiocyanate; imines; imides suchas succinimides and glutimides; imido esters; aziridines; imidates;oxazine; oxazoline; oxazinium; oxazolinium; chlorotriazines;chloropyrimidines; chloroquinoxalines; chlorobenzotriazoles; sulphonylhalides; siloxanes silanols; silanes; pyridyldithio derivatives;N-hydroxysuccinimide esters; activated vinyls and nonactivated vinylsincluding acrylonitriles; acrylic esters; methacrylic esters; crotonicacids; crotonic esters; cinnamic acids; cinnamic esters; styrenes;butadienes; vinyl ethers; vinyl ketones; maleic esters; maleimides;vinyl sulphones; hydrazines; phenyl glyoxal, and combinations thereof.

The bonding agent may also include a linking component disposed betweenand bonding the anchoring component and the functional group. Thelinking component may provide a spacer unit between the anchoringcomponent and the polymerizable functional group. In addition, thelinking component may be configured to aid in dispersing themicrospheres in the matrix and any solvents or co-reactants which may berequired in formation of the final desired material product. In thisregard, the matrix material and solvents, etc., will have a polarity anda hydrogen bonding capacity, and the linking component may be selectedor configured to at least one of: have a polarity compatible with thepolarity of the matrix material, and hydrogen bond with the matrixmaterial.

Some examples of linking components may include, but are not limited toa single bond, a spacer group, and combinations thereof, wherein thespacer group is one of siloxanes, silicones, silicates, esters, ethers,and carbon-based chains including linear, branched and cyclic, saturatedand unsaturated C₁-C₅₀ carbon-based chains, and combinations thereof,wherein the carbon-based chain may be interrupted with at least onehetero atom chosen from sulphur, oxygen, nitrogen, silicon, phosphorus,and combinations thereof, and may comprise a substituent chosen fromhydroxyl, amine, thiol, carbamate, ether, acid, ester, amide, cyano,ureido, and combinations thereof.

The functional components X, may be designed dependent on the matrixmaterial being used and the type of hollow microspheres being used. Anappropriate functional group may be selected that will bind with boththe matrix material and the microsphere. Alternatively, an appropriatefunctional group may be selected that will bind with the matrixmaterial, and an appropriate anchoring group may be selected that willbind with the microspheres. In some embodiments, the functionalcomponent may bind to the anchoring component. In some embodiments, alinking component may be necessary to join the functional component withthe anchoring component. A linking component may be selected that iscapable of being reacted with and bound to each of the selectedfunctional group and anchoring component.

In an embodiment, in a first set of process steps, the linking componentand the anchoring component may be reacted together to attach thelinking component to the anchoring component. In a second set of processsteps, the combined anchoring/linking compound may be reacted togetherwith the functional group to attach the functional group to theanchoring/linking compound to produce the functional component X. Toproduce functionalized microspheres, in a third set of process steps,the microspheres may be reacted with the produced functional componentsX to attach the functional components to the microspheres via theanchoring component.

In an embodiment, the anchoring component may be trimethoxysilyl, thelinking component may be pentyl, and the functional group may be anepoxy. In an embodiment, wherein the microspheres are ceramic, theresultant epoxy/pentyl/trimethoxysilyl functional component may bereacted with the ceramic microspheres to produce functionalizedmicrospheres 15.

In embodiments wherein the microspheres may be ceramic or glass, forexample, prior to surface functionalization preparation, the ceramic orglass hollow microspheres may be treated for about 1 hour in boilingpiranha solution (about 3:1 concentrated H₂SO₄:H₂O₂). After thisetching, the beads may be removed from the piranha bath, rinsed withhigh purity water (such as may be obtained using an Ultrapure Milli-QReagent Water System by Millipore) and dried in a stream of argon ornitrogen. When sufficiently dry, the beads may be modified by any ofseveral different procedures, some of which are discussed below,depending on the desired functional groups to be added to the beads.

In embodiments wherein the microspheres may be polymeric, for example,polyolefins such as polyethylene or polypropylene, the microspheres maybe plasma treated to place hydroxyl moieties on the surface of thespheres. The plasma treated microspheres may be exposed to methacrylicchloride to covalently bind a layer of methacrylate moieties to thesurface of the polymeric microspheres. The modified polymericmicrospheres may be polymerized into polymer networks such aspolyolefins, acrylics, vinylics, and styrene. The plasma treatedmicrospheres may also be treated with isocyanates for addition topolyurethane systems. In this manner, super strong light weight polymercomposites may be made.

EXAMPLES Example 1 Surface Modification with3-methacryloxypropyltrimethoxysilane (Gelest)

Cleaned and dried hollow glass or ceramic microspheres are added to areaction kettle equipped with a mechanical stirrer and immersed in about2% (w/w) 3-methacryloxypropyltrimethoxysilane in anhydrous toluene(Aldrich) for about 24 hours with agitation. The hollow glass or ceramicmicrospheres are filtered and rinsed, for example, with at least thefollowing, or any similar wash sequence: 2 washes with anhydroustoluene, a wash with deionized water, and then a wash with ethanol toremove any physisorbed 3-methacryloxypropyltrimethoxysilane. The hollowglass or ceramic microspheres may be dried in a nitrogen or argonatmosphere. Resulting coverage may be approximately one3-methacryloxypropyltrimethoxysilane/nm² of surface area.

Example 2 Surface Modification with (6-aminohexyl)-triethoxysilane(Gelest)

Cleaned and dried hollow glass or ceramic microspheres are added to areaction kettle equipped with a mechanical stirrer and immersed in about2% (w/w) (6-aminohexyl)-triethoxysilane in anhydrous toluene (Aldrich)for about 24 hours with agitation. The hollow glass or ceramicmicrospheres are filtered and rinsed, for example, with at least thefollowing, or any similar wash sequence: 2 washes with anhydroustoluene, a wash with deionized water, and then a wash with ethanol toremove any physisorbed (6-aminohexyl)-triethoxysilane. The hollow glassor ceramic microspheres are dried in a nitrogen or argon atmosphere.Resulting coverage is roughly one (6-aminohexyl)-triethoxysilane/nm² ofsurface area.

Example 3 Surface Modification with(3-glycidyloxypropyl)trimethoxysilane (Aldrich)

Cleaned and dried hollow glass or ceramic microspheres are added to areaction kettle equipped with a mechanical stirrer and immersed in about2% (w/w) (3-glycidyloxypropyl)trimethoxysilane in anhydrous toluene(Aldrich) for about 24 hours with agitation. The hollow glass or ceramicmicrospheres are filtered and rinsed, for example, with at least thefollowing, or any similar wash sequence: 2 washes with anhydroustoluene, a wash with deionized water, and then a wash with ethanol toremove any physisorbed (3-glycidyloxypropyl)trimethoxysilane. The hollowglass or ceramic microspheres are dried in a nitrogen or argonatmosphere. Resulting coverage is roughly one (3-glycidyloxypropyl)trimethoxysilane/nm² of surface area (FIG. 4).

Example 4 Methacrylate Modified Polyethylene Microspheres

An 8% solution of polyethylene in molten naphthalene is atomized using acommercial paint sprayer. The atomized spheres are collected and thenaphthalene slowly sublimed at 50° C. yielding hollow spheres ofpolyethylene. The hollow polyethylene spheres will be roughly 50 micronsin diameter with a wall thickness of 5-10 microns.

The polyethylene spheres are treated by an oxygen plasma. A gaseous flow(N₂ or N₂+O₂) is created by a continuous pumping (33 m³/h), and excitedby an electrodeless discharge by means of a microwave generator (2450MHz) which delivers an incident power up to 1.5 kW. The discharge isproduced in a quartz tube (32-mm diameter) connected to the fluidizedbed reactor through a 90° elbow. This reactor is constituted of avertical cylindrical Pyrex glass tube (height: h—about 1 m; innerdiameter: D—about 0.15 m) with a porous plate at the bottom to supportthe polyethylene hollow microsphere bed. This plate has to be made witha material that does not destroy the reactive species of the plasma.

The reactor is filled with polyethylene microspheres and the gas feed(N₂ or N₂+O₂) is injected. For low flow rates, the polyethylene spheresdo not move. When the flow increases, the powder starts to be fluidizedand when the pressure counterbalances the weight of the bed,fluidization is initiated. The fluidization of the polyethylene spheresin the reactor occurs for gas flow values equal or above about 0.35Nl/min (for pressure equal or above about 1.9 mbar). For flow valueshigher than about 1.9 Nl/min, there was entrainment of the particles.Prior to plasma treatment, the powder was fluidized by the 0.35 Nl/minflow for 5 min.

The plasma treated hollow microspheres of polyethylene (25 g) are thenadded to a mixture (4:1) of anhydrous toluene and triethylamine, 100 mL,at 0° C. and stirred under an argon atmosphere. Using an additionfunnel, methacrylic acid chloride (Aldrich, 5.0 g) is added dropwise tothe polyethylene microspheres over a period of 25 minutes. The solutionis allowed to stir for three hours and the resulting modified spheresare filtered from solution. The spheres are washed with the mixture oftoluene and triethylamine (3×100 mL) followed by washing with water(3×100 mL). The spheres are then allowed to dry.

Functionalized microspheres 15 having various alternative combinationsof the components as discussed above may be prepared by a manufacturerand retained in bulk for retail to consumers. A consumer may thenpurchase pre-made bulk microspheres for designated purposes, or aconsumer may possibly order a specifically designed microsphere to bemade for their unique purposes. Alternatively, a product manufacturermay provide components in a kit form and include process steps fordesigning functionalized microspheres as needed on site, allowing aconsumer to produce their own functionalized microspheres as needed.

Low-density materials of structural network 50 may be designed andconstructed by selecting appropriate combinations of the variouscomponents as discussed above, including type of matrix material 7, typeof microsphere 10, and configuration of the structural compound X,including the functional component, and, if necessary, the anchoringcomponent, and the linking component. The density of the matrix materialmay thereby be reduced with the incorporation of functionalizedmicrospheres dispersed throughout the material. Because of the covalentbonding and the structural network which results, up to about 80% byweight of the material may be functionalized microspheres, and thematerial may remain sufficiently durable to withstand physical stresses,such as impacts, cracking, rupturing, fatigue, and corrosion. Inembodiments, low-density materials may have various alternative amountsof functionalized microspheres, such as for example, 5% by weight, 10%by weight, 15% by weight, 20% by weight, 25% by weight, 30% by weight,35% by weight, 40% by weight, 45% by weight, 50% by weight, 55% byweight, 60% by weight, 65% by weight, 70% by weight, 75% by weight, or80% by weight, or any amount between any of the listed values.

Low-density structural materials may be made by selecting an appropriatestructural matrix material for the product, and intermixing appropriatefunctionalized hollow microspheres with the matrix material, wherein themicrospheres include at least one functional group selected tocovalently bond with the structural matrix material. The mixture maythen be processed or formed into a desired shape while allowing thehollow microspheres to covalently bond with the matrix material. Formatrix materials, such as polymers, the polymers may be heated to atemperature above the melting temperature of the polymer andappropriately functionalized microspheres may be mixed into the polymermelt to bind with the polymer. The melt may then be injection molded, orextruded, for example, into a desired shaped product, and allowed tocool to produce a resultant material of a reduced weight. For epoxies,appropriately functionalized microspheres may be mixed with a fluidepoxy prior to addition of the hardener. The hardener may then bethoroughly mixed in and the mixture shaped by molding, extrusion orcasting, for example, and allowed to harden into a desired end product.Other types of shaping, molding, or forming processes may also be used,such as, for example, rolling of fluid materials into sheets, to producefinished reduced weight products.

In an embodiment, microspheres for low-density materials may befunctionalized by covalently bonding a bonding agent comprising thefunctional group to microspheres 10 to produce desired functionalmicrospheres 15. The bonding agent may be configured to include ananchor portion for covalently bonding to the microspheres, and thefunctional group for covalently bonding with the matrix material.Functionalizing may further include covalently bonding the anchorportion of the bonding agent to the microspheres. The configuring of thebonding agent may also include configuring the bonding agent to includea linking group which covalently bonds the anchor group with thefunctional group, and the linking group may be chosen to be a componentwhich is dispersible in the matrix material, either due to polarity, orvia hydrogen bonding. Selected constituents may be chosen from any ofthe lists as previously provided, or from any other components, analogsor derivatives which may provide for a structural network of covalentlybound microspheres as described herein.

In an embodiment of a low-density material wherein the matrix materialis an epoxy, the polymerizable functional group may be at least one of:an epoxide, an amide, and an amino; the microsphere may be a ceramicmicrosphere, the anchoring group may be trimethoxysilyl, and the linkingcomponent may be at least one of: pentyl, propyl, hexyl, and steryl. Foran epoxy matrix material, the epoxy may be bisphenol-A diglycidyl etherepoxy with an amine hardener. An amine hardener may be at least one of:ethylene diamine, triethylenetetramine, and a poly(amide).

In an embodiment of a low-density material wherein the matrix materialmay be polyethylene, the polymerizable functional group may be at leastone of an olefin and a vinyl.

In an embodiment of a low-density material wherein the matrix materialmay be acrylic (poly(methyl methacrylate)), the polymerizable functionalgroup may be at least one of a methacrylate and a vinyl.

In an embodiment of a low-density material wherein the matrix materialmay be glass, the polymerizable functional group may be triethoxysilane.

Example 5 General Functionalized Microspheres for an Epoxy Resin

Epoxies are common structural components which have a wide variety ofuses. With reference to FIG. 4, functionalized microspheres for reducingthe density/weight of an epoxy resin are formed from ceramicmicrospheres 10 functionalized to include epoxy polymerizable groupscovalently bonded to the surface thereof. Functional compound X has anepoxy polymerizable group as the functional group, a pentyl chain as thelinking component, and a silane tripod covalently bonded to themicrosphere for anchoring the compound X to the microsphere.

Example 6 A Low-Density Epoxy Resin Kit

A light weight, yet very strong epoxy may be made which uses thefunctionalized microspheres of Example 1. The components for producingthe final epoxy product may be provided in a kit form, which mayinclude, a first epoxy component of bisphenol-A diglycidyl ether epoxy,the functionalized microspheres of Example 1, and a second epoxycomponent of triethylenetetramine hardener. The components may beprovided in amounts which require no additional measuring, wherein thecomponents maybe mixed together in the quantities provided. Oralternatively, proper ratios of portions of the components may becombined for smaller batches.

Example 7 A Light-Weight Epoxy Housing

A variety of products from electric components, housings and containers,to jet aircraft include components which are formed from epoxy resins,and there remains a desire for many of these products to be lighter inweight and stronger. A light weight, yet very strong epoxy housing willbe produced from the kit of Example 6.

Essentially equal parts of the first epoxy component (epoxy afunctionalized microspheres) and the second epoxy component will bemixed with an amount of the functionalized microspheres to produce amixture of about 40 wt % microspheres, to produce an uncured epoxymatrix material. The uncured matrix material will be injected into amold to form a rectangular box-shaped housing component, and theingredients will be allowed to copolymerize and cure to a solid resinthat is extremely strong, but light in weight, wherein the hollowmicrospheres essentially will be part of the epoxy matrix.

Example 8 Method for Producing a Low-Density Epoxy Resin

A liquid epoxy resin (about 20 g, Dow 335, epoxy equivalent weight about200) is mixed with about 10 g of glass hollow microspheresfunctionalized with (6-aminohexyl)-triethoxysilane under vacuum toprevent entrapment of air bubbles. The two components are blendedtogether for about 20 minutes under low shear. The blend is heated toabout 90° C. and liquid 4,4′-methylenedianiline (about 9.5 g, amineequivalent weight about 99) is added and blended in. The resultantmixture is suitable for forming (casting, molding, etc.) into a desiredshape, and will cure to a solid mass having a measured density of about1.03 g/cc.

Example 9 Method for Producing a Low-Density Epoxy Product

A mold is packed with glass hollow microspheres functionalized with(6-aminohexyl)-triethoxysilane and evacuated. Liquid epoxy resin (about20 g, Dow 335, epoxy equivalent weight about 200) is blended with apolyamide hardener Ancamide™ 220-X70 (about 10 g, amine content about170 mg KOH/g) and the blend is injected into the mold under 3000 psi andallowed to cure to yield a molded part with a density of about 0.73g/cc.

Example 10 Method for Producing a Low-Density Epoxy Product

A liquid epoxy resin (about 20 g, Dow 335, epoxy equivalent weight about200) is mixed with about 10 g of glass hollow microspheresfunctionalized with (6-aminohexyl)-triethoxysilane under vacuum toprevent entrapment of air bubbles. The epoxy resin/microsphere mixtureis blended with a polyamide hardener Ancamide™ 220-X70 (about 10 g,amine content about 170 mg KOH/g) and the liquid composite is injectedinto a mold under 3000 psi and allowed to cure to yield a molded parthaving a density of about 1.06 g/cc.

Example 11 Method for Producing a Low-Density Polystyrene

Styrene monomer is passed over an ion exchange resin de-inhibitor columnto remove any inhibitor. Azobisisobutyronitrile (about 3% w/w) is addedto the styrene monomer (about 100 g) and the two are added in a reactionkettle. The system is purged using argon and heated to about 64° C.using a temperature controlled oil bath. The viscosity of the styrenebegins to build after about 15 minutes at which time hollow microspheres(about 25 g) functionalized with 3-methacryloxypropyltrimethoxysilaneare added and blended into the polymerizing styrene system. The systembegins to gel into a solid mass after about 40 minutes at which timesamples are removed under argon. The mixture will solidify into a solidmass after about 1 hour, forming a plastic material having a measureddensity of about 0.85 g/cc.

Example 12 Method for Producing a Low-Density Polystyrene Product

Styrene monomer (about 100 g), azobisisobutyronitrile (about 3% w/w),and hollow microspheres (about 30 g) functionalized with3-methacryloxypropyltrimethoxysilane are mixed together. Polystyrene(about 10 g, MW 100 kDa) is then added to the mixture as a thickener tohelp with suspending the hollow microspheres. A mold is heated to about85° C., evacuated, and the mixture is injected into the mold under 2000psi. The mold temperature is raised to about 100° C. after 30 minutesand then cooled. After cooling the mold is opened to yield a moldedlight weight part having a density of about 0.87 g/cc.

Example 13 Method for Producing a Low-Density Epoxy Coating

Liquid epoxy resin (about 20 g, Dow 335, epoxy equivalent weight about200) is mixed with about 10 g of glass hollow microspheresfunctionalized with (3-glycidyloxypropyl) trimethoxysilane under vacuumto prevent entrapment of air bubbles. The two components are blendedtogether for about 20 minutes under low shear. The epoxyresin/microsphere mixture is blended with a polyamide hardener Ancamide™220-X70 (about 10 g, amine content about 170 mg KOH/g) and the liquidcomposite is diluted with methylethylketone/xylene (about 2:1) until thesystem is about 75% solids. The system is spray applied to steel sheetsto form a light weight coating having a coating density of about 1.01g/cc.

Example 14 Method for Producing a Low-Density Acrylate

A bed of methacrylate functional polyethylene spheres (from Example 4)is created using a silicone form. Methyl methacrylate monomer (Aldrich)is passed through an ion exchange column to remove inhibitor. A UVinitiator (Darocur 1173, 0.25 wt %) is added to the methyl methacrylatemonomer. The monomer is then purged with argon to remove oxygen. Underargon, the monomer is then added to the bed of methacrylate functionalpolyethylene microspheres until the top layer of spheres is justsubmerged. The bed of spheres plus monomer is then placed in an argonfilled UV cabinet and the sample irradiated (280 nm-400 nm light) for 10minutes. The solidified brick is removed from the form and the densitymeasured to be 0.69 g/ml.

Any system described above, may be utilized as coatings, castings, poursand the like. In the examples, a general ratio of about 2/3 hostmaterial and 1/3 beads by volume is provided. However, as discussedearlier, the density of the products may be reduced further byincreasing the bead content. This disclosure is not limited to theparticular systems, devices and methods described, as these may vary.The terminology used in the description is for the purpose of describingthe particular versions or embodiments only, and is not intended tolimit the scope.

In the above detailed description, reference is made to the accompanyingdrawings, which form a part hereof. In the drawings, similar symbolstypically identify similar components, unless context dictatesotherwise. The illustrative embodiments described in the detaileddescription, drawings, and claims are not meant to be limiting. Otherembodiments may be used, and other changes may be made, withoutdeparting from the spirit or scope of the subject matter presentedherein. It will be readily understood that the aspects of the presentdisclosure, as generally described herein, and illustrated in theFigures, can be arranged, substituted, combined, separated, and designedin a wide variety of different configurations, all of which areexplicitly contemplated herein.

The present disclosure is not to be limited in terms of the particularembodiments described in this application, which are intended asillustrations of various aspects. Many modifications and variations canbe made without departing from its spirit and scope, as will be apparentto those skilled in the art. Functionally equivalent methods andapparatuses within the scope of the disclosure, in addition to thoseenumerated herein, will be apparent to those skilled in the art from theforegoing descriptions. Such modifications and variations are intendedto fall within the scope of the appended claims. The present disclosureis to be limited only by the terms of the appended claims, along withthe full scope of equivalents to which such claims are entitled. It isto be understood that this disclosure is not limited to particularmethods, reagents, compounds, compositions or biological systems, whichcan, of course, vary. It is also to be understood that the terminologyused herein is for the purpose of describing particular embodimentsonly, and is not intended to be limiting.

As used in this document, the singular forms “a,” “an,” and “the”include plural references unless the context clearly dictates otherwise.Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. Nothing in this disclosure is to be construed as anadmission that the embodiments described in this disclosure are notentitled to antedate such disclosure by virtue of prior invention. Asused in this document, the term “comprising” means “including, but notlimited to.”

While various compositions, methods, and devices are described in termsof “comprising” various components or steps (interpreted as meaning“including, but not limited to”), the compositions, methods, and devicescan also “consist essentially of” or “consist of” the various componentsand steps, and such terminology should be interpreted as definingessentially closed-member groups.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases at least one and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to embodiments containing only one suchrecitation, even when the same claim includes the introductory phrasesone or more or at least one and indefinite articles such as “a” or an(e.g., “a” and/or “an” should be interpreted to mean “at least one” or“one or more”); the same holds true for the use of definite articlesused to introduce claim recitations. In addition, even if a specificnumber of an introduced claim recitation is explicitly recited, thoseskilled in the art will recognize that such recitation should beinterpreted to mean at least the recited number (e.g., the barerecitation of “two recitations,” without other modifiers, means at leasttwo recitations, or two or more recitations). Furthermore, in thoseinstances where a convention analogous to “at least one of A, B, and C,etc.” is used, in general such a construction is intended in the senseone having skill in the art would understand the convention (e.g., “asystem having at least one of A, B, and C” would include but not belimited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, and/or A, B, and Ctogether, etc.). In those instances where a convention analogous to “atleast one of A, B, or C, etc.” is used, in general such a constructionis intended in the sense one having skill in the art would understandthe convention (e.g., “a system having at least one of A, B, or C” wouldinclude but not be limited to systems that have A alone, B alone, Calone, A and B together, A and C together, B and C together, and/or A,B, and C together, etc.). It will be further understood by those withinthe art that virtually any disjunctive word and/or phrase presenting twoor more alternative terms, whether in the description, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” will be understood to include thepossibilities of “A” or “B” or “A and B.”

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, such as in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” and the like include the number recited andrefer to ranges which can be subsequently broken down into subranges asdiscussed above. Finally, as will be understood by one skilled in theart, a range includes each individual member. Thus, for example, a grouphaving 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, agroup having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells,and so forth.

Various of the above-disclosed and other features and functions, oralternatives thereof, may be combined into many other different systemsor applications. Various presently unforeseen or unanticipatedalternatives, modifications, variations or improvements therein may besubsequently made by those skilled in the art, each of which is alsointended to be encompassed by the disclosed embodiments.

What is claimed is:
 1. Functionalized hollow microspheres for reducingthe density of a structural matrix material, the functionalized hollowmicrospheres comprising: at least one hollow microsphere comprising atleast one anchoring group covalently bonded to a surface of themicrosphere; at least one functional group configured to covalently bondwith the structural matrix material; and a linking component covalentlybonding the at least one anchoring group with the at least onefunctional group, wherein the linking component is selected from linear,branched, cyclic, substituted, unsubstituted, saturated, and unsaturatedC₁-C₅₀ carbon-based chains, and combinations thereof.
 2. Thefunctionalized hollow microspheres of claim 1, wherein the microspherescomprise organic polymers.
 3. The functionalized hollow microspheres ofclaim 1, wherein the microspheres are plastic.
 4. The functionalizedhollow microspheres of claim 1, wherein the microspheres are selectedfrom the group comprising: ceramic, glass, metal, carbon compositions,metalloids, and combinations thereof.
 5. The functionalized hollowmicrospheres of claim 1, wherein the at least one functional group ischosen from acrylates, methacrylates, ethacrylates, 2-phenyl acrylates,acrylamides, methacrylamides, cyanoacrylates, epoxies, oxetanes, vinyls,vinyl ethers, vinyl esters, vinyl amides, vinyl ketones, styrenes,styryls, isocyanates, uranyls, carboxyls, olefins, allyls, allyl ethers,allyl esters, allyl amines, allyl amides, ethynyls, propargyls,acryloyls, methacryloyls, maleic anhydride, maleic esters, maleimides,itaconates, silanes, siloxanes, silanols, titanates, thiols,phosphazines, titanium oxides, silicones, zirconium oxides, andcombinations thereof.
 6. The functionalized hollow microspheres of claim1, wherein the at least one functional group is configured to covalentlybond with the structural matrix material selected from the groupcomprising thermoplastic resins, thermoset resins, inorganic matrices,cementitious matrices, and combinations thereof.
 7. The functionalizedhollow microspheres of claim 1, wherein the at least one anchoring groupis chosen from alcohols; amines; thiols; thiosulphates; carboxylicacids; acid chlorides; esters; acetals; hemiacetals; aminals;hemiaminals; ketones; aldehydes; α-hydroxy ketones; α-halo ketones;epoxides; lactones; thiolactones; azalactones; isocyanate; thiocyanate;imines; succinimides; glutimides; imido esters; aziridines; imidates;oxazine; oxazoline; oxazinium; oxazolinium; chlorotriazines;chloropyrimidines; chloroquinoxalines; chlorobenzotriazoles; sulphonylhalides; siloxanes; silanols; silanes; pyridyldithio derivatives;N-hydroxysuccinimide esters; activated vinyls; nonactivated vinyls;acrylonitriles; acrylic esters; methacrylic esters; crotonic acids;crotonic esters; cinnamic acids; cinnamic esters; styrenes; butadienes;vinyl ethers; vinyl ketones; maleic esters; maleimides; vinyl sulphones;hydrazines; phenyl glyoxal, and combinations thereof.
 8. Thefunctionalized hollow microspheres of claim 1, wherein the linkingcomponent is selected to enhance dispersion of the microspheres in thestructural matrix material.
 9. The functionalized hollow microspheres ofclaim 1, wherein the structural matrix material has a polarity and ahydrogen bonding capacity, and the linking component is selected to haveat least one of: a polarity compatible with the polarity of thestructural matrix material, and a hydrogen bond with the structuralmatrix material.
 10. The functionalized hollow microspheres of claim 1,wherein: the microspheres are one of glass microspheres, ceramicmicrospheres or plastic microspheres; and the microspheres comprise atleast one functional group configured to covalently bond with thestructural matrix material selected from the group comprisingthermoplastic resins, thermoset resins, inorganic matrices, cementitiousmatrices, and combinations thereof.
 11. The functionalized hollowmicrospheres of claim 10, wherein: the at least one functional group ischosen from acrylates, methacrylates, ethacrylates, 2-phenyl acrylates,acrylamides, methacrylamides, cyanoacrylates, epoxies, oxetanes, vinyls,vinyl ethers, vinyl esters, vinyl amides, vinyl ketones, styrenes,styryls, isocyanates, uranyls, carboxyls, olefins, allyls, allyl ethers,allyl esters, allyl amines, allyl amides, ethynyls, propargyls,acryloyls, methacryloyls, maleic anhydride, maleic esters, maleimides,itaconates, silanes, siloxanes, silanols, titanates, thiols,phosphazines, titanium oxides, silicones, zirconium oxides, andcombinations thereof; and the at least one anchoring group is chosenfrom alcohols; amines; thiols; thiosulphates; carboxylic acids; acidchlorides; esters; acetals; hemiacetals; aminals; hemiaminals; ketones;aldehydes; α-hydroxy ketones; α-halo ketones; epoxides; lactones;thiolactones; azalactones; isocyanate; thiocyanate; imines;succinimides; glutimides; imido esters; aziridines; imidates; oxazine;oxazoline; oxazinium; oxazolinium; chlorotriazines; chloropyrimidines;chloroquinoxalines; chlorobenzotriazoles; sulphonyl halides; siloxanes;silanols; silanes; pyridyldithio derivatives; N-hydroxysuccinimideesters; activated vinyls; nonactivated vinyls; acrylonitriles; acrylicesters; methacrylic esters; crotonic acids; crotonic esters; cinnamicacids; cinnamic esters; styrenes; butadienes; vinyl ethers; vinylketones; maleic esters; maleimides; vinyl sulphones; hydrazines; phenylglyoxal, and combinations thereof.
 12. A low-density material comprisingfunctionalized hollow microspheres covalently bonded with a structuralmatrix material, wherein the functionalized hollow microspherescomprise: at least one hollow microsphere comprising at least oneanchoring group covalently bonded with a surface of the microsphere; atleast one functional group covalently bonded with the structural matrixmaterial; and a linking component covalently bonding the at least oneanchoring group with the at least one functional group, wherein thelinking component is selected from linear, branched, cyclic,substituted, unsubstituted, saturated, and unsaturated C₁-C₅₀carbon-based chains, and combinations thereof.
 13. The low-densitymaterial of claim 12, wherein the microspheres are dispersed throughoutthe structural matrix material.
 14. The low-density material of claim12, wherein the microspheres comprise up to about 80% of the weight ofthe low-density material.
 15. The low-density material of claim 12,wherein the low-density material has a density lower than the structuralmatrix material.
 16. The low-density material of claim 12, wherein themicrospheres comprise inorganic solids.
 17. The low-density material ofclaim 12, wherein the microspheres are selected from the groupcomprising: ceramic, glass, metal, carbon compositions, metalloids, andcombinations thereof.
 18. The low-density material of claim 12, whereinthe structural matrix material is a thermoplastic resin.
 19. Thelow-density material of claim 18, wherein the thermoplastic resin isselected from the group comprising: polyvinyl chloride, polyethylene,polypropylene, polyethylene terephthalate, acrylic, acetal, nylon,polytetrafluoroethylene, urethane, urea, carbonate, sulfone, cyclics,polybutylene terephthalate, other rigid engineering polymers, andcombinations thereof.
 20. The low-density material of claim 12, whereinthe structural matrix material is a thermoset resin.
 21. The low-densitymaterial of claim 20, wherein the thermoset resin is selected from thegroup comprising: polyester, vinylester, epoxy, acrylic, phenolic,sulfone, phenyl-formaldehyde, melamine, melamine-formaldehyde, otherrigid thermoset engineering polymers, and combinations thereof.
 22. Thelow-density material of claim 12, wherein the structural matrix materialis an inorganic matrix.
 23. The low-density material of claim 22,wherein the inorganic matrix is selected from the group comprising:ceramic, glass, glass-ceramic, sol-gel compositions, and combinationsthereof.
 24. The low-density material of claim 12, wherein thestructural matrix material is a cementitious matrix.
 25. The low-densitymaterial of claim 24, wherein the cementitious matrix is selected fromthe group comprising: portland cement, gypsum, polymer modified cement,latex modified cement, epoxy cements, other cementitious materialscommonly used in the manufacture or repair of concrete structure, andcombinations thereof.
 26. The low-density material of claim 12, whereinthe linking component is selected to be dispersible in the structuralmatrix material.
 27. The low-density material of claim 12, wherein theat least one anchoring group is chosen from alcohols; amines; thiols;thiosulphates; carboxylic acids; acid chlorides; esters; acetals;hemiacetals; aminals; hemiaminals; ketones; aldehydes; α-hydroxyketones; α-halo ketones; epoxides; lactones; thiolactones; azalactones;isocyanate; thiocyanate; imines; succinimides; glutimides; imido esters;aziridines; imidates; oxazine; oxazoline; oxazinium; oxazolinium;chlorotriazines; chloropyrimidines; chloroquinoxalines;chlorobenzotriazoles; sulphonyl halides; siloxanes; silanols; silanes;pyridyldithio derivatives; N-hydroxysuccinimide esters; activatedvinyls; nonactivated vinyls; acrylonitriles; acrylic esters; methacrylicesters; crotonic acids; crotonic esters; cinnamic acids; cinnamicesters; styrenes; butadienes; vinyl ethers; vinyl ketones; maleicesters; maleimides; vinyl sulphones; hydrazines; phenyl glyoxal, andcombinations thereof.
 28. The low-density material of claim 12, whereinthe at least one functional group is chosen from acrylates,methacrylates, ethacrylates, 2-phenyl acrylates, acrylamides,methacrylamides, cyanoacrylates, epoxies, oxetanes, vinyls, vinylethers, vinyl esters, vinyl amides, vinyl ketones, styrenes, styryls,isocyanates, uranyls, carboxyls, olefins, allyls, allyl ethers, allylesters, allyl amines, allyl amides, ethynyls, propargyls, acryloyls,methacryloyls, maleic anhydride, maleic esters, maleimides, itaconates,silanes, siloxanes, silanols, titanates, thiols, phosphazines, titaniumoxides, silicones, zirconium oxides, and combinations thereof.